The short answer

A replica of the 720.025 is a lookalike, not a mechanical twin. The genuine reference is the platinum A. Lange & Söhne Lange 1 Tourbillon Perpetual Calendar, a manual-wind watch that combines a one-minute tourbillon with a full perpetual calendar. No replica maker reproduces that movement. What the better factories build is a case and dial that photograph well from a normal distance, plus a real Chinese-made tourbillon and a set of calendar discs that work, just not the way a true perpetual calendar works. The cheaper builds use quartz or basic automatic movements with cosmetic displays.

If you understand that gap going in, you can judge a rep on its own terms: how the tourbillon actually runs, whether the calendar readouts change by themselves, and how the case finishing holds up in daylight.

What the real 720.025 is

Lange introduced the Lange 1 Tourbillon Perpetual Calendar in 2012, and the 720.025 is the platinum version. Roughly 42 mm across, manual winding, calibre L082.1, with the tourbillon carrying a stop-seconds mechanism so you can set it to the second. The calendar side is the interesting part: the signature outsize date, a month indication that runs around the edge of the dial on a ring, moonphase, and a leap-year display, with recessed correctors set into the case band.

Two things matter for anyone comparing a replica to the original. First, the case metal. Platinum reads cooler and duller than steel, and it is noticeably heavy. Second, the calendar logic. A perpetual calendar knows that February has 29 days in a leap year and needs no correction until 2100. That is a gear-train problem, and it is the single hardest thing to fake.

How the tiers differ

Entry tier (under about $200)

• Quartz or low-grade automatic movement
• Tourbillon cage that is often a rotating decorative disc, or a static cutout
• Calendar discs printed on, or a single day/date wheel that skips rather than tracks
• Mineral glass, chromed brass markers, case finishing that looks flat in sunlight

Mid tier (roughly $300 to $900)

• Real Chinese flying tourbillon, usually 60 seconds per rotation
• Working day, date and month displays, but not perpetual: you adjust after short months
• Moonphase disc on a 29.5-day or 24-hour cycle depending on the module
• Sapphire crystal on the better builds, decent polished lugs, corrector pushers that actually move

Upper tier ($1,200 and up)

• Reinforced or upgraded tourbillon with smoother regulation and better finishing
• Calendar module that handles 30 and 31-day months automatically in most examples
• Hand-finished movement plates, blued screws, engraved balance cock
• Heavier case, correct proportions, and closer dial print

None of these, including the top tier, is a true perpetual calendar. Some sellers describe them as one. The leap-year indicator is usually the tell: on a genuine watch it advances through a four-year cycle, and on most replicas it is either fixed or moves on a 12-month loop.

Checks I would run before paying

• Ask for a video of the tourbillon running with the watch flat, not a photo. You want to see one clean rotation per minute with no stutter.
• Set the date to the 31st, let it pass, and see whether the month and day follow. This exposes a cosmetic calendar in seconds.
• Check the correctors in the case band. Press each one with a plastic peg and confirm it changes the matching display. Cosmetic pushers are common on cheap builds.
• Use the moonphase as a rough test. Advance it and see if the disc moves smoothly and whether the disc edge is crisp or blurred.
• Look at the dial print under a loupe or strong light. The outsize date font is the classic failure point, along with the spacing of the text on the dial.
• Flip it. On the real watch you get an untreated German silver three-quarter plate with Glashütte ribbing, blued screws and gold chatons. On replicas you often get rhodium-plated brass with laser stripes. That is fine at the mid tier, but do not pay upper-tier money for a printed plate.
• Ask about water resistance, and then ignore the answer. Any tourbillon rep should be treated as splash-resistant at most.

Finishing and proportion notes

Platinum is a soft, dense metal and the original has a particular grey-white tone that stainless steel does not match. Reps generally look a shade brighter and shinier. That is unavoidable, so judge the case on other things: does the bezel take a clean polish, do the lugs taper correctly into the strap, is the crown the right size and does it screw down without grit.

The dial of the 720.025 is busy in a way most people underestimate. The outsize date, the month ring, the moonphase and the offset time display all compete for attention, and if the print on one element is off, the whole thing reads as fake at a glance. I would rather have a rep with slightly less accurate engraving and sharp dial work than the reverse.

Living with it

Two rules. Do not set the date or use the correctors between roughly 9 p.m. and 3 a.m., because the calendar train is engaged and you can shear a tooth. And expect to correct the calendar yourself after February and after any 30-day month, since the module is not perpetual. The moonphase will also drift if the disc runs on a 24-hour cycle rather than a lunar one.

Servicing is the other reality. Chinese tourbillons can be regulated and lubricated by a competent watchmaker, but parts are not sitting on shelves, so a broken tourbillon often means a replaced movement rather than a repair. Budget for that when the price looks tempting.

Before you order

Check the seller's actual photos instead of catalogue renders, confirm the case size against your wrist, and find out what happens if the movement arrives dead. Replica sales are restricted or illegal in some countries and shipments can be seized, so know where you stand locally. And keep the purchase in perspective: this is a design piece that costs a fraction of the original, not an investment.